The day the ‘death spiral’ died

As small technology companies and major generator-retailers test virtual power plants of various types around Australia it’s worth looking back a few years at United Energy’s award-winning trial which proved it was possible to manage peak demand. EcoGeneration looks back at the lucky 13 who led the way in Melbourne.

The orchestration of networks of scattered, disparate solar PV generation and storage is being spoken of as a powerful solution to the problem of sluggish electricity supply meeting unpredictable spikes in demand.

If power stored and generated at homes and factories can be directed to the market when it really, really needs it, some of the nasty consequences of supply failure can be avoided. Trials are afoot in Adelaide with AGL’s virtual power plant and on a more sophisticated level with experiments in peer-to-peer energy trading by Power Ledger in Perth and the GreenSync’s ARENA-funded Distributed Energy Exchange, or deX, in Victoria and the ACT.

But let’s turn back the clock a few years and look at United Energy’s work in Melbourne in 2014, where its virtual power plant of a handful of solar PV sites won it the Clean Energy Council’s 2016 Innovation Award.

The project ran around the time the “death spiral” was a hot topic of fearful conversation around the watercoolers at the headquarters of electricity networks, the logic being that rising electricity prices would see more consumers convert to solar and go off the grid … so that prices for remaining customers would rise higher … so that more consumers go off the grid … so that prices for remaining customers rise higher … so that more consumers leave the grid, and so on and so on.

“That was quite a different environment to what we see today,” says Karl Edwards, manager customer innovation and growth at Victorian network United Energy.

Lucky 13

The objective for United Energy in 2014 was to learn about solar and storage, their impact on residential consumption and how that would affect a network provider. The trial was also expected to help energy retailers understand whether exported residential solar energy was a viable way to manage peak demand on the four or five super-hot days that strike the region each year.

The trial included the installation of 5kW of solar and 10kWh storage in 13 households randomly dotted around the network, from as far up as Balwyn North all the way down to Flinders.

It was a nervous start. Would the 13 rooftop PV generators be on-call to export as instructed by the project team and, on the extremely hot days when they were most needed, would the batteries still work? “At the time a lot of the systems on the market weren’t rated at those temperatures by the manufacturers … [but] we didn’t want to sit around and wait 10 years for another hot summer,” Edwards says.

The Sunverge lithium ion batteries were tested in rented lab space where the summer of 2009 – which included three consecutive days that peaked above 43°C – was re-enacted using heat lamps. “That gave us the confidence this technology could be used,” he says.

With the gear in place, the team pushed the button. “We operated all the units as a virtual plant and they all operated together and exported,” says Edwards. At peak times of the afternoons the units were instructed to discharge in order to reduce load at each location; households were also programed to consume up to a limit of kilowatt-hours for a set period.

Myth in the bin

On the lead-up to a peak day, batteries were prepared to be fully charged so that during the day they would be relied on for self-consumption and to export until they were fully discharged. If the following day wasn’t expected to be a peak demand day, the system would revert to operation which maximised self-consumption so that any excess solar would fill the battery.

The participants weren’t expected to make any changes to their usage and the installed technology at the 13 households is still in operation today, Edwards says.

“On non-peak days they are still optimising for solar self-consumption, and when we forecast peak event days [above 40°C] on the network those units still continue to operate in that mode to maximise battery discharge.”

The trial was a success: the systems could operate on extremely hot days and discharge as directed. And as the team watched data for self-consumption stream in as summer turned to winter, it also busted the myth of the “death spiral”.

“With this level of solar and storage it’s just not feasible for customers to disconnect from the grid,” Edwards says. “From what we saw, for a number of months in the middle of winter even with 5 or 10kW of solar panels on a house and a substantially sized battery you wouldn’t have sufficient energy for a customer to get through those winter months.”